Polythematic fantasia in 4 sections. Quite typical variation from archetype is seen in section proportions.

III is quite long (16 bars) otherwise a pattern: Long, short, long, short in approx 2:1 ratios. Tonal answers are used in the 2nd section. Transposed Dorian mode… yet the majority of cadences are still on D.
Section III needs special comment, the rest is quite regular. 1) Alto is left out of exposition of 3a 2) Section III divides into 3 parts (i) exposes 3a; (ii) Is a transition to 3b (which is only a farshortened version of 3a) and (iii) Exposes 3b “properly”. 3) The process of (i) & (ii) is virtually identical in concept although quite different in actual notes.